The Iron Streets of Pompeii Author(S): Eric E
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The Iron Streets of Pompeii Author(s): Eric E. Poehler, Juliana van Roggen and Benjamin M. Crowther Source: American Journal of Archaeology , Vol. 123, No. 2 (April 2019), pp. 237-262 Published by: Archaeological Institute of America Stable URL: https://www.jstor.org/stable/10.3764/aja.123.2.0237 JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at https://about.jstor.org/terms Archaeological Institute of America is collaborating with JSTOR to digitize, preserve and extend access to American Journal of Archaeology This content downloaded from 130.237.165.40 on Wed, 30 Sep 2020 17:32:02 UTC All use subject to https://about.jstor.org/terms The Iron Streets of Pompeii , , Includes Supplementary Content Online In July 2014, we conducted a survey of Pompeii’s street network to document traces of iron that were observed on the stone-paved streets, which resulted in the identification of 434 instances of solid iron and iron staining among the paving stones. This paper de- scribes the iron deposits, categorizing them into six observable types, and argues that, in the final days and weeks before the eruption of Mount Vesuvius in 79 C.E., Pompeians werein addition to using solid iron wedgespouring molten iron and iron slag onto their streets as a method of emergency repair. Before discussing the evidence available for how the melting, transporting, and depositing of these ferric materials might have been accomplished, we address whether the Romans had the technical ability to achieve suf- ficiently high temperatures to melt iron, finding much evidence to affirm the claim that they did. Finally, we consider why Pompeians undertook such measures to repair their streets. Recent research on the costs of paving stone streets in terms of time, money, and opportunity provides the economic context for this novel repair process and shows the use of iron and iron slag to have been an expedient alternative.1 By the late first century C.E., within only decades of the Roman conquest of Britain, the iron-rich region of the Weald was already producing more than 550 tons of wrought iron annually,2 making it one of the largest iron production sites within the Roman empire.3 Extracting the raw iron from the stone ore that encased it required reducing the ore to a slurry so that a viscous sponge-like bloom of iron collected within the furnace, while the re- maining materials were liquefied and drawn off as slag. Later, the bloom was reheated and hammered to remove remaining impurities and give shape to the metal. The bloomery process, however, was surprisingly inefficient and a significant percentage of the iron, from 40% to 70%, remained in the slag, 1 e authors would like to extend their thanks to Massimo Osanna and the superinten- dency and custodians of Pompeii for providing access to conduct this research. e Pom- peii Quadriporticus Project and Pompeii Archaeological Research Project: Porta Stabia also provided years of infrastructural support. We are also grateful to e Five Colleges, Inc., for early funding through their Digital Humanities Fellows program and to the anon- ymous reviewers for the AJA who helped us improve this paper. Special thanks belong to American Journal of Archaeology Mark Robinson, who walked Pompeii’s streets with us to examine many iron deposits and Volume 123, Number 2 whose challenges and encouragements were of the greatest value. e Supplementary Ta- ble for this article can be found online at hps://works.bepress.com/eric-poehler/107/. April 2019 Figures are the authors’ own unless otherwise noted. Pages 237–62 2 Cleere 1976; Cleere and Crossley 1985; Rackham 2001, 40–1. DOI: 10.3764/aja.123.2.0237 3 See Pleiner (2000, 41–7) for an overview. Craddock (2008, 108) reports the annual iron output of the Roman Empire was 82,500 tons, but see Sim (2011, 22–3) for other www.ajaonline.org estimates. This content downloaded from 130.237.165.40 on Wed, 30 Sep 2020 17:32:02 UTC All use subject to https://about.jstor.org/terms . which the ironworkers subsequently deposited in enormous waste piles.4 In some cases, this waste mate- rial was recycled or repurposed for building material; the largest example of reuse of slag was as paving for long stretches of the London-Lewes Way in Sussex. Averaging 4.5 m to 5.5 m wide and as much as 0.35 m deep, the slag covered more than 30 km of roadway, an amount that Straker and Margary calculate to be no less than 35,000 tons.5 Over decades of exposure and use, one stretch of the roadway, near Holtye, became oxidized and fused into a single, seamless, ferrous mass (fig. 1). The deep ruts found worn into this surface were likely created by the iron rims of wagon wheels made of the very metal separated from the slag paving. This is England’s great iron road, a curious artifact and testament to the scale of industry in the imperial age. Only a few other routes paved with slag are known from antiquity. These include a second road in Britain (in the Forest of Dean), this one connecting a mine and production facilities.6 Elsewhere, Roman cities such as Cardiff (Wales) and Rouen (France) paved some of their urban streets in slag. In fact, at Rouen the practice was widespread; multiple streets were covered with . London-Lewes Way, a Roman road near Holtye, Sussex, slag, including one street that Romans paved in this paved in iron slag (Margary 1965, frontispiece). fashion multiple times.7 While slag paving is rare, deep ruts are a famous aspect of Roman roads everywhere. Investigations at Pompeii have shown that particularly erroneous, belief that Romans could not achieve tem- high volumes of traffic concentrated in narrow streets peratures necessary to melt iron.9 To explore the use of could wear down even a stone-paved surface in only a iron in Pompeian streets, we first describe our method few decades. One option for repair, complete repav- of study and our classification of the more than 400 ing in stone, was a difficult and expensive endeavor instances of iron used in solid and in liquid forms in that might block important through routes in a city Pompeii’s streets. Next, we address the technical fea- for months.8 Research by the authors has revealed that sibility of such a process and attempt to reconstruct the Pompeians devised another option that was inge- where and how it might have been accomplished. In nious and unconventional: after heating iron or iron- the final section, we attempt to answer to why such an rich slag to a molten state, they poured out hundreds unusual procedure was undertaken. of individual repairs onto, into, and below the paving The primary unit of our analysis is the individual de- stones of the city’s most important streets. This claim posit of iron or ferric material. We have divided these is controversial not only for the novelty of such a pro- deposits into six types. The online supplementary cedure but also because of the commonly held, but table Description of Iron Deposits (at https://works. bepress.com/eric-poehler/107/) presents these data.10 4 Tylecote 1986, 175–76; Craddock 2003, 233; Saredo Paro- di 2013, 18–22; Pérez Macias et al. 2014, 15–9. 9 Specialists in metallurgy have long been disabused of this 5 Straker and Margary 1938, 58. On calculating slag heaps belief (e.g., Read 1934, 545–46), but modern reference works more recently, see Humphris and Carey 2016. continue to repeat the idea (e.g., Humphrey et al. 1998, 218). 6 Pleiner 2000, 45, 267. Davies (1935, 90) notes slag-paved Even in 2012, the Oxford Classical Dictionary entry on metal- roads in Normandy near Mayenne and Tourouvre (Mézières). lurgy states that iron could not be melted until the 19th century 7 Deglatigny 1931, 177, 185, 187–90, 195, 208–9; Davies (OCD 2012, 939). 1935, 90–1; Schubert and Ingen Housz 1957, 41 n. 2. 10 is article’s online supplementary content is hosted by the 8 Poehler and Crowther 2018, 599–601. University of Massachuses Amherst’s institutional repository. This content downloaded from 130.237.165.40 on Wed, 30 Sep 2020 17:32:02 UTC All use subject to https://about.jstor.org/terms References in figure captions and footnotes to specific Consolare), the mid 19th century (e.g., Via Stabiana), iron deposits use the format “ID_[number].” Some and the early 20th century (e.g., Via dell’Abbondanza). deposits contain solid iron remnants. Others are rep- This fact demonstrates that the use of iron and iron resented only by a stain on the paving stones, and we slag was an ancient phenomenon and not an early cannot be certain if these deposits were formed from modern intervention. Moreover, the locations of these iron metal, highly ferric slag, or some combination of ferric deposits are too specific and too frequent to have the two. We therefore refer to deposits generally as been accidental. “iron/iron slag” or “ferric materials” to acknowledge In total, the survey documented 434 occurrences of that ambiguity. Throughout the discussion, we refer ancient iron in the streets at Pompeii.